Jim,
I'm truely disappointed about your response. If this newsgroup is about
showing off how big your dick is, go right ahead. I was under the impression
that the newsgroup was to discuss and provide help. None of the information
I gave is wrong, I provided a fair warning to think twice before putting a
UHF antenna enclosed inside a frame. You made it into a ****ing match. I
admire the knowledge you have, but the way you display it makes me sick.
Rob
(The Netherlands, not a native English speaker, sorry for any spelling
mistakes...).
"Jim Weir" wrote in message
...
"Rob Turk"
shared these priceless pearls of wisdom:
-"Jim Weir" wrote in message
.. .
- Are you guessing on this, repeating an OWT, or do you have first hand
hard
-data?
-
- Jim
-
-
-As a licensed ham operator
Jesus. A ham operator? Those are the credentials you come to the table
with?
Amateur radio extra, first licensed in 1959. First 'phone with radar
endorsement, 1960. BS-Physics (Microwave option) 1967. MSEE CGS 1983, RF
option. Pacific Southwest Airlines (1963-1967) avionics and radar
technician.
Teledyne Ryan Space Systems (1967-1973) Microwave Antenna Engineer.
Founder and
CEO RST Engineering, with a world class reputation for hidden antennas in
nonconductive structures (1973 --) with approximately fifteen THOUSAND
operating
antennas in plastic/wood/fabric aircraft including one hanging in the
Smithsonian.
I have sufficient experience with frequencies
-around 1200 MHz.
How long has it been since you fell off the turnip truck, feller? The ham
bands
at 33 and 23 cm are 10% or so away from the transponder frequencies. Not
too
far away, but far enough.
Those don't like their antenna's shielded by wet or painted
-surfaces.
First, the plural is "antennas", not the possessive. In the second place,
this
is the first mistake of fact so far. That is just horsepuckey. Wet and
paint
won't make squat for difference. And I've done and retained the
engineering
data that says so.
Transponders are just over 1000MHz
1030 and 1090 to be exact. Betcha can't tell me without looking which one
is
transmit and which one is receive.
, it's reasonably safe to assume
-they are equally influenced. I'm not saying it will never work (fwiw,
GSM at
-900MHz works in-door), but I do want to caution people that there are
many
-variables involved that could make it not work.
Yada, yada yada...
-
-Contrary to COM signals (118-136MHz) you can't use just any CB or VHF
SWR
-meter to check out if the antenna matches at these frequencies. With the
-transponder sending out pulses of 200+ Watts I wouldn't want to gamble
-having a bad SWR and seeing that power end up ruining the transponder
stage.
-Better be safe and put the $22 antenna where it belongs; Outside.
Izzat a fact? Then I guess I'd best trash my $50k worth of RF antenna
test
equipment, because I surely wouldn't want to gamble my transponder on
brothers
Hewlett and Packard's equipment and the results derived therefrom.
By the way, do the math before you post. That 200+ watts of transponder
power
is peak pulse power. If you go through the calculation, you find that the
transponder output stage is running about 5 watts CW averaged over a
couple of
seconds or so.
Now, to repeat what I've been telling my colleagues building airplanes for
the
last 30 years...put the transponder antenna inside the plastic with a
round or
(better yet) octagonal ground plane, shield the sensitive parts of your
anatomy
with tinfoil, and go for it.
Jim
Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com